sedimentary

Chert / Flint

Silicon Dioxide (Microcrystalline Quartz, SiO2)

Hardness: 7 on the Mohs scale, Color: Varies widely from gray, brown, yellowish-brown, to reddish, Luster: Waxy to vitreous, Crystal structure: Microcrystalline / Cryptocrystalline (chalcedony), Cleavage: None (exhibits conchoidal fracture), Specific Gravity: 2.60 to 2.65

Identified August 5, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed via the chemical or biochemical precipitation of silica from aqueous solutions, often replacing carbonate rocks (limestone or chalk) in marine environments over millions of years.

Uses & applications

Historically used for making stone tools, arrowheads, and spark generation in firearms. Modern uses include abrasives, decorative landscape stones, and occasionally lapidary work.

Geological facts

Chert is extremely durable and resistant to weathering, which is why prehistoric stone tools made from flint survive so well in the archaeological record.

Field identification & locations

Identify in the field by its conchoidal fracture (sharp, curved edges when broken), waxy luster, and high hardness that scratches glass easily. Commonly found in limestone and chalk formations worldwide.

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